Vapor generator



Jan. 21, 1964 .1. J. BANKER ETAL 3,118,431

I VAPOR GENERATOR Filed May 17, 1961 5 Sheets-Sheet l V FIG.1

Jo J. Banker In %1/m-- ATTORNEY Jan. 21, 1964 J. J. BANKER ETAL 3,118,431

VAPOR GENERATOR Filed May 1", 1961 5 Sheets-Sheet 2 INVENTORS Jo J. Banke r ATTORNEY Jan. 21, 1964 .1. J. BANKER ETAL 3,118,431

VAPOR GENERATOR Filed May 17, 1961 5 Sheets-Sheet 5 -FIG.3-

l i i g v I NVENTOR.S

Hllary Mohs y W|ll1am A. 'Drab= Jogn J. Banker I 1/ AT TORNEY.

Jan. 21, 1964 J. J. BANKER ETAL 5 Sheets-Sheet 4 FIG. 4

IN VEN TORS Hilary Mohs A. Drab Jan. 21, 1964 Filed May 1'7, 1961 J. J. BANKER ETAL VAPOR GENERATOR 5 Sheets-Sheet 5 INVENTORS Hilary Mohs William A. Drab Jo J. Banker A-TTORNVEY 3,118,431 VAPOR GENERATOR John J. Banker, Cranford, N.J., William A. Drab, Oyster Bay, N.Y., and Hilary F. Mohs, Orange, N.J., assignors to The Bahcocli 8: Wilcox Company, New York, N.Y.,

a corporation of New Jersey Filed May 17, 1%1, Ser. No. 110,671 7 Claims. (Cl. 122333) This invention relates in general to steam generators and more particularly to steam generating units of the type especially adapted for use in marine installations.

Todays demands for faster ships are coupled, through necessity, with urgent requirements to reduce construction, operating and maintenance expenses. To meet these needs, marine type steam generators should have the attributes of high availability and efliciency, should fit easily and conveniently within a minimum of fireroom space, should operate with a high degree of dependability for long periods of time, with low maintenance and with a minimum of personnel, and should be light in weight.

In the accomplishment of these objectives the present invention is directed to a marine type steam generator possessing the virtues of compactness, portability, simplicity, reliability and ability to provide eificient operation at high ratings with a low draft loss and a minimum of physical size for the output achieved. The steam generator of the invention is further characterized by' a completely water-cooled integral furnace so constructed and arranged as to eliminate furnace brickwork and its attendant maintenance problem; all fluid supply and steam generating tubes terminating in the steam and water drums, thereby eliminating headers, and so constructed and arranged as to minimize the variety of tube configurations and bends, thus saving in the cost of fabrication and erection and minimizing the variety of tubes required as spares; an arrangement of fuel burning provisions and a furnace construction permitting the burning of the fuel at high rates of heat release per cubic foot of furnace volume; its readiness upon delivery to be skidded or lifted onto the foundation, hooked up and placed in operation, thereby further saving in cost of building and erection; and its ability to respond to wide and frequent load swings.

The invention provides for a marine type steam generator comprising an upper spheroidal steam and water drum having a lower portion formed in the shape of a hemisphere and a lower spheroidal 'Water drum having an upper portion formed in the shape of a hemisphere. An upright vessel of substantially circular horizontal crosssection extends between and is connected in pressure tight relation to the upper and lower drums, with an upright combustion chamber being disposed concentrically within the vessel and arranged to receive fuel and combustion air. A substantially circular wall is disposed between the combustion chamber and the vessel and cooperates with the combustion chamber to form an arcuate gas pass thereabout occupied by a bank of steam generating tubes and communicating with the combustion chamber. The circular wall also cooperates with the upright vessel to define an annular space which is maintained under an air pressure at least equal to the gas pressure in the combustion chamber to counterbalance the outward thrust of the heating gases exerted on the inside of the boundary walls of the gas pass. All of the water supply and steam generating tubes of the unit are similarly formed and have their upper and lower ends respectively directly and radially connected to the upper and lower drums, thus minimizing the variety of tube configurations and bends and eliminating the use of headers.

The various features of novelty which characterize our invention are pointed out with particularity in the United States Patent claims annexed to and formingfa part of this specificae,

tion. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred embodiment of the invention.

Of the drawings:

FIG. 1 is a partly diagrammatic sectional elevation of a steam generator constructed and operable in accordance with the invention and taken along the line 1--1 of FIG. 2;

FIG. 2 is a plan view taken along the line 2-2 of FIG. 1;

FIG. 3 is a sectional elevation taken along the line 3-3 of FIG. 2;

FIG. 4 is a sectional plan view of a modified steam generator construction;

FIG. 5 is a fragmentary sectional elevation taken along the line 5-5 of FIG. 4.

In the drawings the invention has been illustrated as embodied in a shop-assembled bottom-supported natural circulation marine type steam generating unit designed principally for oil firing and for furnace operation under internal gaseous pressures above atmospheric pressure; and available in standard sizes for loads ranging up to 200,000 lbs. of steam per hour at pressures up to 1200 p.s.i. and at temperatures ranging from the saturation temperature corresponding to the pressure to 900 F. with the use of a superheater. Preassembly of the components of the unit in the factory assures a better quality finished unit, minimizes the time and effort required at the project site to place the unit in service, and assures optimum performance. The unit requires no prepared foundation other than a deck of suflicient strength, and no skilled labor for making the few connections required to place it in service.

The steam generating unit shown in FIGS. 1-3 comprises an upper spheroidal steam and water drum 10 having a lower portion 10A formed in the shape of a hemisphere and an upper hemispheroidal portion ltlB formed with a steam outlet 11 at its top and with an access opening which is fitted with a manhole plate 13; and a lower spheroidal water drum 12 having an upper portion 12A formed in the shape of a hemisphere and arranged with its vertical axis in the same vertical plane as the vertical axis of the upper drum 10 and a lower hemispheroidal portion 12B formed with an access opening at its bottom which is fitted with a manhole plate 15. The use of spheroidal drums allows installation of the steam generator in a variety of positions relative to the longitudinal axis of the ship. This in contrast to the conventional two drum marine type steam generator wherein the horizontally arranged cylindrical'drums must be located with the longitudinal axes of the drums in a fore and aft position to prevent circulation difficulties during heavy rolling or pitching of the ship. The upper and lower drums are connected by fluid conducting tubes constructed and arranged as hereinafter described. Most of the pressure parts of the unit are contained by insulation-covered metallic casing 14 forming an upright vessel 16 of substantialiy circular horizontal cross-section extending between and connected at its upper and lower ends in pressuretight relation to the upper and lower drums, with the intermediate portion 14A of the casing formed in the shape of a cylinder and the upper and lower portions, 148 and 14C, of the casing being of frusto-conical form and respectively converging in the direction of the upper and lower drums. The space within the vessel 16 is divided by walls 18 and 20 into a combustion chamber 22, a pair of upright arcuate gas passes 24, 26, and an upright annular space 28 for air under pressure. Combustion chamber 22 is substantially circular in horizontal l 'atended Jan. 21,

cross-section, has its vertical axis in the same vertical plane as the vertical axes of the upper and lower drums and 12, occupies the central portion of the vessel 16, is formed by the top and bottom portions, respectively, of the drums 12 and 10 and by the wall 20, and has an axially elongated gas outlet 29 formed in the boundary wall and Opening to a common gas inlet for the supply of heating gases to the arcuate gas passes 24 and Wall 18 is made of metallic casing having cylindrical and frusto-conical portions corresponding to and spaced from those of the casing 14, with the walls 14 and 18 cooperating to form the annular air space 28 therebetween. The lower end of the annular space 28 is closed by the drum portion 12A and by a horizontally arranged annular metallic plate 34 which is secured to the casing 14 and disposed in overlapping relation with and secured to an annular plate 36 welded to the hemispherical portion of the drum 12, while the upper end of the space 28 is closed by the drum portion 10A and by a horizontally arranged arcuate metallic plate 37 secured to the easing 14 and disposed in overlapping relation with and secured to an arcuate plate welded to the drum portion 10A.

The arcuate gas passes 24 and 26 extend in opposite angular directions from the common gas inlet 30 to positions near to and on opposite sides of a circular burner port 31 formed in the wall 20, are disposed about the combustion chamber 22, and are formed by the walls 18 and 20, by the top and bottom portions, respectively, of the drums 12 and 10, and by upright end plates 33. Each plate 33 extends radially inward from the Wall 18 to the wall 20 and is secured to the drums 10 and 12 at its upper and lower ends and to the wall 18. Each of the arcuate gas passes communicates at its outlet end with a metal conduit 32 of circular cross-section extending through the upper irusto-conical portion 143 of the easing 14 in sealing relation therewith and having its inlet end registering with an opening formed in the upper frusto-conical portion of casing 18. The outlet ends of the conduits 32 are connected to a common fiue, not shown, for conducting the heating gases to another heat trap, if desired, or to the stack.

The arcuate gas passes 24 and 26, as well as the common gas inlet 30, are occupied by an upright fluid heating tube bank 42 comprising radially spaced arc-shaped rows of upwardly extending tubes of relatively small diameter positioned across the flow of gases in the gas inlet 30 and the gas passes 24 and 26. The last few rows of tubes of the bank 42 in the low gas temperature end of gas passes 24 and 26 serve as downcomers or fluid supply tubes; while all of the remaining tubes of the bank 42 are steam generating tubes. The tubes of the bank 42 extend generally parallel to and have a contour corresponding to the shape of the casing 18 and have their inlet ends directly and radially connected to the lower drum portion 12A and their outlet ends directly and radially connected to the upper drum portion 10A. The tubes 42 are preferably of 1% inches outside diameter. The relatively small diameter of these tubes, together with the cross-flow of gases thereover, provide optimum rates of heat transfer from the hot gases to the fluid in the tubes. The rapid flow of heat through the tubes to the small column of fluid in each tube makes the unit a notably fast steamer, capable of readily handling sudden load changes. Except in the gas outlet zones of the gas passes 24 and 26, most of the intermediate portions of the two rows of tubes next adjacent the outer row of tubes of the bank 42 are so bent as to occupy the intert'ube spaces of the outer row of tubes and to contact, along with the outer row of tubes, the metallic casing 18, thereby providing fluid cooling of such casing.

Wall 20 cooperates with the upper portion of the drum 12 and the lower portion of the drum It to form the combustion chamber 22 and comprises a row of relatively widely spaced steam generating tubes 44 which are studded to support refractory closing the intertube spaces and have their upper and lower ends directly and radially connected to the hemispherical portions of the upper and lower drums 10 and 12, respectively. Wall tubes 44 have a configuration similar to the tubes of the tube bank 42 and thus provide a combustion chamber having an intermediate portion of cylindrical form and upper and lower portions of frusto-conical form respectively converging in the direction of the upper and lower drums. Tubes 44A of the wall 20 are left bare in most part to provide the gas outlet 29 and cooperate with an arcuate row of widely spaced steam generating tubes 45 to form a screen 23 for the heating gases discharging from the combustion chamber 22. Tubes 45 of the screen 23 occupy a portion of the common gas inlet 30, have a configuration similar to the tubes of the tube bank 42, and have their opposite ends directly and radially connected to the hemispherical portions of the drums 10 and 12. Tubes 44 and screen 23 are of relatively small outside diameter, preferably 2 inches, to promote high rates of heat transfer. The portion of the drums 10 and 12 in the combustion chamber zone are protected from excessive heat by refractory 46.

The steam generator is bottom-supported by structural steel members including a ribbed annular cradle 49 disposed about and secured to the lower portion of the drum 12 and adapted to be carried by and secured to the ship foundation.

Water is supplied to the steam generating tubes of the tube bank 42, wall tubes 44, and screen tubes 23 by the downcorner tubes of the tube bank 42 and by downcomer tubes 47 symmetrically arranged on opposite sides of the port 31 and disposed in the space 28 adjacent the end plates 33. Tubes 47 have a configuration similar to that of the steam generating tubes and have their upper and lower ends directly and radially connected to the upper drum portion 10A and the lower drum portion 12A, respectively.

The fluid cooled combustion chamber 22 is especially intended for the burning of a liquid fuel at extremely high rates of heat release. To this end intermediate portions of some of the tubes 44 are suitably bent and covered with refractory to form the burner port 31 which opens to the cylindrical portion of the combustion chamber 22 at a position diametrically opposite the gas outlet 29 and has oppositely tapering inner and outer portions arranged in converging relation to provide intimate mixing of incoming liquid fuel and air. The combustion chamber 22 is fired by a horizontally disposed liquid fuel burner 48 which extends through a cover plate 50 secured to the casing 14 and which has its discharge end located co-axially within the port 31 and arranged to direct a finely atomized steam of liquid fuel radially into the combustion chamber 22. The burner and combustion chamber are proportioned and arranged to prevent flame impingement on the boundary wall 20, to yield a turbulence that will cause uniform gas temperature and gas composition across the gas outlet 29, and to provide a flow path of sutficient length to insure complete combustion. The tubes in the immediate vicinity of the port 31 are backed with refractory 51 and metallic casing 52 which extends between the drums 10 and 12 and the end plates 33 and is formed with an opening which registers with the inlet end of the port 31.

Combustion air for the fuel burner 48 is supplied from a forced draft fan, not shown, to the space 28 by way of a rectangular conduit 56 opening to the space 28 through which the air flows to an air register 60 in which a circular series of pivoted air doors are arranged for regulating the supply of air delivered to the port 31 and for imparting a degree of rotation to the air stream. The conduit 56 opens to the space 28 through the wall 14, has its upright sides at its discharge end flared in the direction of the wall 14, and is occupied by a bell-shaped air distributor 55 closed at both ends, with the distributor having its base contacting the casing 18 and its sides flaring in the direction of the casing 18 and cooperating with the sides of the conduit 56 and the Walls 14 and 18 to divide the incoming air into parallel streams which flow in opposite angular directions through the space 23 to the register 69. While the high pressure air flows from the conduit 56 to the register 60, the space 28 is maintained by this air under a pressure higher than the heating gas pressure at any point along its flow path, so that any leakage through the wall 18 will be inward toward the gas flow path rather than outward to avoid the blasting of the hot gases on the wall 14. In addition, the air is preheated as it passes through the space 28 to the register 60, since it flows along the hot metallic casing 18 and over the downcomer tubes 47 before entering the register 60.

The heating gases resulting from the combustion of fuel and air introduced into the combustion chamber 22 flow through the gas outlet 29 and over the screen 23 to the common gas inlet 34), then divide into parallel streams which flow reversely in opposite angular directions and in generally horizontal arcuate paths of travel through the gas passes 24 and 26 and over the steam generating tubes 42 positioned therein to the gas outlet conduits 32.

With the steam generator constructed as described, feedwater enters the drum and flows downwardly in parallel through the downcomer tubes 47 and the downcomer tubes of the tube bank 42 to the drum 12 which supplies fluid in parallel flow relation to the steam generating tubes of the tube bank 42, the tubes of the screen 23, and wall tubes 44, from all of which the stream and water mixtures generated discharge to the drum 10. Saturated steam discharges fromthe drum through the outlet 11, and thence to the point of use.

In the embodiment of the invention illustrated in FIGS. 4 and 5, the construction and arrangement of the steam generator is generally the same as that shown in FIGS. l3, except in the particulars hereinafter described, and accordingly for convenience and clarity the same reference characters are utilized to identify identical or closely similar parts.

In the modified form all of the gases leaving the combustion chamber fiow through a single arcuate gas pass, the combustion chamber is fired by two vertically spaced burners, only one of which is shown, and the upstream portion of the arcuate gas pass is occupied by a superheater. Accordingly, the gas outlet 29 formed in the wall of the combustion chamber 22 is located adjacent to and is formed in part by one of the end plates 33. So the end plates 33, the walls 26 and 18, and the upper and lower portions of the drums 12 and 10, respectively, cooperate to form an upright arcuate gas pass having an inlet 25A communicating with the gas outlet 29 of the combustion chamber and an outlet communicating with a circular metal conduit 37 of the same character as the conduits 32 of the embodiment previously described. The end plate 33 at the gas outlet 29 is protected from the high temperature gases by refractory and a row of radially spaced steam generating tubes 42A. Tubes 44A are left bare in most part to provide the gas outlet 29 and cooperate with tubes 45A, which are located in the gas inlet 25A, to form a screen for the heating gases discharging from the combustion chamber to the gas pass 25. A superheater 62 is disposed in the arcuate gas pass 25 at a position near to the gas outlet 28; while the remaining portion of the gas pass 25 is occupied by the tube bank 42 which is situated downstream gas-Wise of the superheater 62. All of the tubes of the bank 42 are steam generating tubes except forthe last few rows of tubes, with respect to gas flow, which serve as downcomer or fluid supply tubes. Superheater 62 comprises nested multilooped horizontally extending tubes arranged in vertically spaced platens to define parallel flow paths for steam flow in parallel flow heat transfer relation with the gases and extending between vertical inlet and outlet headers 64 and 66, respectively, disposed externally of the wall 18 and in the space 28, with the header 64 having its upper inlet end connected by a conduit 68 to the steam space of the drum 1t) and with the header 66 having an outlet 79 at its lower end. The casing 18 in the vicinity of the superheater 62 is formed with an opening which is fitted With removable insulation-lined panels 72 for access to the superheater tubes; while the wall 14 is suitably formed to provide a housing 74 for the headers 64 and 66 having removable access panels 76.

The combustion chamber is fired by two horizontally disposed vertically spaced liquid fuel burners 48 arranged to discharge atomized liquid fuel streams radially into the cylindrical portion of the combustion chamber 22. After leaving the combustion chamber 22 the heating gases are directed through the gas pass 25 and consecutively over the screen tubes 44A, 45A, the superheater 62 and the steam generating tube bank 42, and thence discharge to the gas outlet conduit 37.

Steam and water mixtures generated in the tubes 42, screen tubes 44A, 45A, and wall tubes 44 discharge to the drum 10. Saturated steam is supplied from the drum 10 to the superheater inlet header 64 by tubular conduit 68, the steam then passing through the superheater tubes to the outlet header 66 for discharge to the point of use by way of the outlet 70.

As in the first described embodiment, all of the water supply and steam generating tubes have their opposite ends directly and radially connected to the upper and lower drums to exclude headers and are similarly formed to reduce to a minimum the variety of tube configurations and bends.

While in accordance with the provisions of the statutes we have illustrated and described herein the best form and mode of operation of the invention now known to us, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that certain features of our invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. A natural circulation steam generating unit comprising an upper spheroidal steam and water drum having a lower portion formed in the shape of a hemisphere, a lower spheroidal water drum having an upper portion formed in the shape of a hemisphere, means forming an upright vessel connected to and extending between said upper and lower drums, means including the hemisphere portions of said drums and a row of upwardly extending steam generating tubes forming an unobstructed upright combustion chamber disposed in and occupying the entire central portion of said vessel and extending between said drums, wall means disposed between said vessel and combustion chamber and cooperating with said combustion chamber to form an upwardly elongated gas pass therebetween and with said vessel to form a space therebetween for air under pressure, a steam generating tube bank in said gas pass including upwardly extending tubes disposed across the flow of gases therein, all of the steam generating tubes of the unit having their upper ends di'- rectly connected to the lower hemisphere portion of said upper drum and their lower ends directly connected to the upper hemisphere portion of said lower drum, tubular conduit means for supply of fluid to said steam generating tubes having their upper ends directly connected to said upper drum and their lower ends directly connected to said lower drum, all of the steam generating tubes having a similar configuration, means for introducing fuel and air into said combustion chamber, while maintaining an air pressure in said space at least equal to the gas pressure in said combustion chamber, gas outlet means from said combustion chamber opening to said gas pass at a position upstream gas-wise of said tube bank, and means forming a gas exit through said wall means and vessel and opening to said gas pass at a position downstream gas-wise of said tube bank.

2. A natural circulation steam generating unit comprising an upper spheroidal steam and water drum having a lower portion formed in the shape of a hemisphere, a lower spheroidal water drum having an upper portion formed in the shape of a hemisphere, means forming an upright vessel connected to and extending between said upper and lower drums, means including the hemisphere portions of said drums and a row of upwardly extending steam generating tubes forming an unobstructed upright combustion chamber of substantially circular horizontal cross-section disposed in and occupying the entire central portion of said vessel and extending between said drums, wall means disposed between said vessel and combustion chamber and cooperating with said combustion chamber to form an upwardly elongated gas pass therebetween and with said vessel to form a space therebetween for air under pressure, a steam generating tube bank in said gas pass including upwardly extending tubes disposed across the flow of gases therein, all of the steam generating tubes of the unit having their upper ends directly connected to the lower hemisphere portion of said upper drum and their lower ends directly connected to the upper hemisphere portion of said lower drum, tubular conduit means for supply of fluid to said steam generating tubes having their upper ends directly connected to the lower hemisphere portion of said upper drum and their lower ends directly connected to the upper hemisphere portion of said lower drum, burner means for introducing fuel and air into said combustion chamber, while maintaining an air pressure in said space at least equal to the gas pressure in said combustion chamber, gas outlet means from said combustion chamber disposed diametrically opposite said burner means and opening to said gas pass at a position upstream gaswise of said tube bank, and means forming a gas exit through said wall means and vessel and opening to said gas pass at a position downstream gas-wise of said tube bank.

3. A natural circulation steam generating unit comprising an upper spheroidal steam and water drum having a lower portion formed in the shape of a hemisphere, a lower spheroidal water drum having an upper portion formed in the shape of a hemisphere, means forming an upright vessel of substantially circular horizontal cross section connected in pressure-tight relation to and extending between said upper and lower drums, means including the hemisphere portions of said drums and a row of upwardly extending steam generating tubes forming an upright combustion chamber of substantially circular horizontal cross-section disposed in the central portion of said vessel, wall means disposed between said vessel and combustion chamber and cooperating with said combustion chamber to form an upwardly elongated arcuate gas pass therebetween and with said vessel to form an annular space therebetween for air under pressure, a steam generating tube bank in said gas pass including upwardly extending tubes disposed across the fiow of gases therein, all of the steam generating tubes of the unit having their upper ends directly and radially connected to the lower hemisphere portion of said upper drum and their lower ends directly and radially connected to the upper hemisphere portion of said lower drum, downcomer tubes for supply of fiuid to said steam generating tubes disposed outside of the gas flow path and having their upper ends directly connected to the lower hemisphere portion of said upper drum and their lower ends directly connected to the upper hemisphere portion of said lower drum, means for introducing fuel and air into said combustion chamber, while maintaining an air pressure in said space at least equal to the gas pressure in said combustion chamber, a gas outlet from said combustion opening to said gas pass at a position upstream gas-wise of said tube bank, and means forming a gas exit through said wall means and vessel and opening to said gas pass at a position downstream gas-wise of said tube bank.

4. A natural circulation bottom-supported marine steam generating unit comprising an upper spheroidal steam and water drum having a lower portion formed in the shape of a hemisphere, a lower spheroidal water drum having an upper portion formed in the shape of a hemisphere, means forming an upright vessel of substantially circular horizontal cross-section connected in pressuretight relation to and extending between said upper and lower drums, means including the hemisphere portions of said drums and a row of upwardly extending steam generating tubes forming an upright combustion chamber of substantially circular horizontal cross-section disposed concentrically within said vessel, wall means disposed between said vessel and combustion chamber and cooperating with said combustion chamber to form an upwardly elongated arcuate gas pass therebetween and with said vessel to form an annular space therebetween for air under pressure, a steam generating tube bank in said gas pass including radially spaced arc-shaped rows of upwardly extending tubes disposed across the How of gases therein, all of the steam generating tubes of the unit having their upper ends directly and radially connected to the lower hemisphere portion of said upper drum and their lower ends directly and radially connected to the upper hemisphere portion of said lower drum, downcomer tubes for supply of fluid to said steam generating tubes disposed in said annular air space and having their upper ends directly and radially connected to the lower hemisphere portion of said upper drum and their lower ends directly and radially connected to the upper hemisphere portion of said lower drum, means for introducing fuel and air into said combustion chamber, while maintaining an air pressure in said space at least equal to the gas pressure in said combustion chamber, a gas outlet from said combustion opening to said gas pass at a position upstream gas-wise of said tube bank, and means forming a gas exit through said wall means and vessel and opening to said gas pass at a position downstream gas-wise of said tube bank.

5. A natural circulation bottom-supported steam generating unit comprising an upper spheroidal steam and water drum having a lower portion formed in the shape of a hemisphere, a lower spheroidal water drum having an upper portion formed in the shape of a hemisphere, means forming an upright vessel of substantially circular horizontal cross-section connected in pressure-tight relation to and extending between said upper and lower drums, means including the hemisphere portions of said drums and a row of upwardly extending steam generating tubes forming an unobstructed upright combustion chamber of substantially circular horizontal cross-section disposed concentrically within and occupying the entire central portion of said vessel and extending between said drums, wall means disposed between said vessel and combustion chamber and cooperating with said combustion chamber to form an upwardly elongated arcuate gas pass therebetween and with said vessel to form an annular space therebetween for air under pressure, a steam generating tube bank in said gas pass including radially spaced arc-shaped rows of upwardly extending tubes disposed across the flow of gases therein, all of the steam generating tubes of the unit having their upper ends directly and radially connected to the lower hemisphere portion of said upper drum and their lower ends directly and radially connected to the upper hemisphere portion of said lower drum, downcomer tubes for supply of fluid to said steam generating tubes disposed in said annular air space and having their upper ends directly and radially connected to the lower hemisphere portion of said upper drum and their lower ends directly and radially connected to the upper hemisphere portion of said lower drum, all

of the steam generating tubes having a similar configuration, means for introducing fuel and air into said combustion chamber, while maintaining an air pressure in said space at least equal to the gas pressure in said combustion chamber, gas outlet means from said combustion opening to said gas pass at a position upstream gas-wise of said tube bank, and means forming a gas exit through said wall means and vessel and opening to said gas pass at a position downstream gas-wise of said tube bank.

6. A natural circulation steam generating unit comprising an upper spheroidal steam and water drum having a lower portion formed in the shape of a hemisphere, a lower spheroidal water drum having an upper portion formed in the shape of a hemisphere, means forming an upright vessel connected in pressure-tight relation to and extending between said upper and lower drums, means including the hemisphere portions of said drums and a row of upwardly extending steam generating tubes forming an unobstructed upright combustion chamber of substantially circular horizontal cross-section disposed in and occupying the entire central portion of said vessel and extending between said drums, wall means disposed between said vessel and combustion chamber and cooperating with said combustion chamber to form a pair of upwardly elongated gas passes therebetween having a common gas supply inlet and with said vessel to define a space therebetween for air under pressure, a steam generating tube bank in at least one of said gas passes including upwardly extending tubes disposed across the flow of gases therein, all of the steam generating tubes of the unit having their upper ends directly connected to the lower hemisphere portion of said upper drum and their lower ends directly connected to the upper hemisphere portion of said lower drum, tubular conduit means for supply of fluid to said steam generating tubes having their upper ends directly connected to the lower hemisphere portion of said upper drum and their lower ends directly connected to the upper hemisphere portion of said lower drum, burner means for introducing fuel and air into said combustion chamber, while maintaining an air pressure in said space at least equal to the gas pressure in said combustion chamber, gas outlet means from said combustion chamber disposed diametrically opposite said burner means and opening to said common gas supply inlet of said gas passes, and means forming a pair of gas exits extending through said Wall means and vessel and each opening to the gas discharge end of a corresponding one of said gas passes.

7. A natural circulation steam generating unit comprising an upper spheroidal steam and water drum having a lower portion formed in the shape of a hemisphere, a lower spheroidal water drum having an upper portion formed in the shape of a hemisphere, means forming an upright vessel connected in pressure-tight relation to and extending between said upper and lower drums, means including the hemisphere portions of said drum and a row of upwardly extending steam generating tubes forming an unobstructed upright combustion chamber disposed in and occupying the entire central portion of said vessel and extending between said drums, wall means disposed between said vessel and combustion chamber and cooperating with said combustion chamber to form an upwardly elongated gas pass therebetween and with said vessel to define a space therebetween for air under pressure, a steam generating tube bank in said gas pass including upwardly extending tubes disposed across the flow of gases therein, all of the steam generating tubes of the unit having their upper ends directly connected to the lower hemisphere portion of said upper drum and their lower ends directly connected to the upper hemisphere portion of said lower drum, tubular conduit means for supply of fiuid to said steam generating tubes having their upper ends directly connected to the lower hemisphere portion of said lower drum, a superheater in said gas pass connected for steam flow from said upper -drum, all of the steam generating tubes having a similar configuration, means for introducing fuel and air into said combastion chamber, while maintaining an air pressure in said space at least equal to the gas pressure in said combustion chamber, gas outlet means from said combustion chamber opening to said gas pass at a position upstream gas-wise of said tube bank, and means forming a gas exit through said wall means and vessel and opening to said gas pass at a position downstream gas-wise of said tube bank.

References Cited in the file of this patent UNITED STATES PATENTS 2,044,270 Wood June 16, 1936 2,567,696 Kessler Sept. 11, 1951 2,944,532 Frisch et a1. July 12, 1960 

1. A NATURAL CIRCULATION STEAM GENERATING UNIT COMPRISING AN UPPER SPHEROIDAL STEAM AND WATER DRUM HAVING A LOWER PORTION FORMED IN THE SHAPE OF A HEMISPHERE, A LOWER SPHEROIDAL WATER DRUM HAVING AN UPPER PORTION FORMED IN THE SHAPE OF A HEMISPHERE, MEANS FORMING AN UPRIGHT VESSEL CONNECTED TO AND EXTENDING BETWEEN SAID UPPER AND LOWER DRUMS, MEANS INCLUDING THE HEMISPHERE PORTIONS OF SAID DRUMS AND A ROW OF UPWARDLY EXTENDING STEAM GENERATING TUBES FORMING AN UNOBSTRUCTED UPRIGHT COMBUSTION CHAMBER DISPOSED IN AND OCCUPYING THE ENTIRE CENTRAL PORTION OF SAID VESSEL AND EXTENDING BETWEEN SAID DRUMS, WALL MEANS DISPOSED BETWEEN SAID VESSEL AND COMBUSTION CHAMBER AND COOPERATING WITH SAID COMBUSTION CHAMBER TO FORM AN UPWARDLY ELONGATED GAS PASS THEREBETWEEN AND WITH SAID VESSEL TO FORM A SPACE THEREBETWEEN FOR AIR UNDER PRESSURE, A STEAM GENERATING TUBE BANK IN SAID GAS PASS INCLUDING UPWARDLY EXTENDING TUBES DISPOSED ACROSS THE FLOW OF GASES THEREIN, ALL OF THE STEAM GENERATING TUBES OF THE UNIT HAVING THEIR UPPER ENDS DIRECTLY CONNECTED TO THE LOWER HEMISPHERE PORTION OF SAID UPPER DRUM AND THEIR LOWER ENDS DIRECTLY CONNECTED TO THE UPPER HEMISPHERE PORTION OF SAID LOWER DRUM, TUBULAR CONDUIT MEANS FOR SUPPLY OF FLUID TO SAID STEAM GENERATING TUBES HAVING THEIR UPPER ENDS DIRECTLY CONNECTED TO SAID UPPER DRUM AND THEIR LOWER ENDS DIRECTLY CONNECTED TO SAID LOWER DRUM, ALL OF THE STEAM GENERATING TUBES HAVING A SIMILAR CONFIGURATION, MEANS FOR INTRODUCING FUEL AND AIR INTO SAID COMBUSTION CHAMBER, WHILE MAINTAINING AN AIR PRESSURE IN SAID SPACE AT LEAST EQUAL TO THE GAS PRESSURE IN SAID COMBUSTION CHAMBER, GAS OUTLET MEANS FROM SAID COMBUSTION CHAMBER OPENING TO SAID GAS PASS AT A POSITION UPSTREAM GAS-WISE OF SAID TUBE BANK, AND MEANS FORMING A GAS EXIT THROUGH SAID WALL MEANS AND VESSEL AND OPENING TO SAID GAS PASS AT A POSITION DOWNSTREAM GAS-WISE OF SAID TUBE BANK. 